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Microstructural investigation of the Carancas meteorite

Published online by Cambridge University Press:  11 November 2010

Kani Rauf ,
Anthony Hann ,
Chandra Wickramasinghe  and
Barry E. DiGregorio
Kani Rauf*
Affiliation:
Cardiff Centre for Astrobiology, Cardiff University, Cardiff CF10 3DY, UK
Anthony Hann
Affiliation:
School of Biosciences, Cardiff University, Cardiff CF10 3US, UK
Chandra Wickramasinghe
Affiliation:
24 Llwynypia Road, Lisvane, Cardiff CF14 0SY, UK
Barry E. DiGregorio
Affiliation:
Cardiff Centre for Astrobiology, Cardiff University, Cardiff CF10 3DY, UK
*
e-mail: kanidawan@yahoo.com
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Abstract

Particles in the Carancas meteorite were examined by electron microscopy (transmission electron microscopy/scanning electron microscopy), energy dispersive analysis of X-rays (EDAX) and Fourier Transform Infrared spectroscopy. Scanning electron microscopical observations reveal that the particles of variable sizes have a stony appearance. Many of these particles show fractures in places, thus confirming an ealier observation that the meteorite was subjected to a high-velocity impact. The outer rim of many aggregates displays a mud crack-like texture. At high magifications, this texture shows ovoid and elongated features, which appear similar to microfossils found in other meteorites.

As revealed by both scanning and transmission electron microscopy, some particles show three clearly marked zones, distinguishable by their differences in electron density and texture: a light zone, a dark zone and an intermediate zone. The EDAX analysis of these particles shows that the light zone is composed of silicates rich in Fe, Ni and S (the elements of troilite and pentlandite). The dark zone contains high concentrations of Mg and Si (the major elements of high-temperature minerals, such as forsterite, Mg2SiO4 and enstatite, MgSiO3) intermixed with carbonates and traces of Al, Ca and Na. The intermediate zone also contains high-temperature minerals and Fe-Ni rich silicates.

The Carancas meteorite produces an infrared waveband showing prominent features of some carbonate species, amorphous and crystalline silicates, and olivine groups. Hydrated silicates and hydroxyl groups are less abundant, as shown by the presence of small humps between 2.5 and 8.0 μm.

The abundance of high-temperature minerals and iron-rich metal confirms an earlier observation that the meteorite is an ordinary H4/5 chondrite. Some particles in the Carancas meteorite are found to have structural and chemical characteristics similar to those of the 81P/Wild 2 comet.

Keywords

81P/Wild 2 cometCarancas meteoriteenergy dispersive analysis of X-raysFourier Transform Infrared spectroscopyH4/5 chondritescanning electron microscopytransmission electron microscopy
Type
Research Article
Information
International Journal of Astrobiology , Volume 10 , Issue 2 , April 2011 , pp. 105 - 112
Copyright
Copyright © Cambridge University Press 2010

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